ABB REG316 4 Series Operating Instructions Manual page 254

ABB Switzerland Ltd
Notes:
Only the voltages of similar sources that have coincident am-
·
plitudes and phase-angles and are connected to the same
busbar should be compared.
Wherever possible the voltages should also be processed by
neighbouring sampling devices and the same analogue input
unit. The purpose of this is to limit signal conditioning errors
should the power system frequency deviate from the rated
frequency f and during transients. To prevent false tripping
N
during extreme variations of frequency, either the pick-up
setting can be increased or the balanced voltage function can
be blocked by a frequency function.
Differing primary rated voltages of the v.t's can be com-
·
pensated by appropriately setting the reference values of the
corresponding A/D channels. The adjusted reference values
then apply for all the protection functions connected to the
same channels.
Application example:
R S T V.t. 1
Blocking
input
V.t. 2
Fig. 3.5.22.2 Three-phase balanced voltage scheme (one
measured voltage failed)
3-216
REG 316*4 1MRB520049-Uen / Rev. F
Line 1
Voltage comparsion
function
(three-phase)
Line 2
U
1R
Protection/
U
instrumentation
1S
equipment
U
1T
1
Blocking
input
TRIP-Line 1
TRIP-Line 2
Blocking
input
U
2R
Protection/
U
2S instrumentation
equipment
U
2T
2
HEST 915 010 C
TRIP